Generally, the process for manufacturing integrated circuits on a silicon wafer substrate typically involves deposition of a thin dielectric or conductive film on the wafer using oxidation or any of a variety of chemical vapor deposition processes; formation of a circuit pattern on a layer of photoresist material by photolithography; placing a photoresist mask layer corresponding to the circuit pattern on the wafer; etching of the circuit pattern in the conductive layer on the wafer; and stripping of the photoresist mask layer from the wafer. Each of these steps, particularly the photoresist stripping step, provides abundant opportunity for organic, metal and other potential circuit-contaminating particles to accumulate on the wafer surface.
In the semiconductor fabrication industry, minimization of particle contamination on semiconductor wafers increases in importance as the integrated circuit devices on the wafers decrease in size. With the reduced size of the devices, a contaminant having a particular size occupies a relatively larger percentage of the available space for circuit elements on the wafer as compared to wafers containing the larger devices of the past. Moreover, the presence of particles in the integrated circuits compromises the functional integrity of the devices in the finished electronic product. Currently, mini-environment based IC manufacturing facilities are equipped to control airborne particles much smaller than 1.0 μm, as surface contamination continues to be of high priority to semiconductor manufacturers. To achieve an ultraclean wafer surface, particles must be removed from the wafer, and particle-removing methods are therefore of utmost importance in the fabrication of semiconductors.
The most common system for cleaning semiconductor wafers during wafer processing includes a series of tanks which contain the necessary cleaning solutions and are positioned in a “wet bench” in a clean room. Batches of wafers are moved in sequence through the tanks, typically by operation of a computer-controlled automated apparatus. Currently, semiconductor manufacturers use wet cleaning processes which may use cleaning agents such as deionized water and/or surfactants. Other wafer-cleaning processes utilize solvents, dry cleaning using high-velocity gas jets, and a megasonic cleaning process, in which very high-frequency sound waves are used to dislodge particles from the wafer surface. Cleaning systems which use deionized (DI) water currently are widely used in the industry because the systems are effective in removing particles from the wafers and are relatively cost-efficient. Approximately 4.5 tons of water are used for the production of each 200-mm, 16-Mbit, DRAM wafer.
FIG. 2 illustrates a typical conventional spin-type cleaning tool 8, which includes a spray nozzle 9 positioned above a rotatable substrate support 11. As a wafer substrate 12 is rotated on the substrate support 11, the spray nozzle 9 sprays cleaning liquid streams 10 at high pressure against the surface of the substrate 12 to remove particles 13 from the substrate 12. While most of the particles 13 are effectively removed from the substrate 12 by the high-pressure cleaning liquid streams 10, some of the particles 13 are temporarily ejected from the surface of the substrate 12 and fall back onto the substrate 12. If these particles remain on the substrate 12 after the cleaning process, the particles 13 may contaminate devices fabricated on the substrate 12.
A typical conventional batch-type, or wet bench, cleaning tool for wafers is generally indicated by reference numeral 1 in FIG. 1, and includes a cleaning chamber 2 defining a chamber interior 3. A wafer substrate 5 is submerged in a suitable cleaning fluid 4 in the chamber interior 3, such that the cleaning fluid 4 dissolves and removes organic film, such as photoresist, from the surface of the substrate 5. Unlike the spin-type cleaning tool 8, the conventional batch-type cleaning tool 1 is effective in preventing re-deposition of removed particles back onto the substrate 5. However, one of the problems frequently encountered in use of the conventional batch-type cleaning tool 1 is that the organic photoresist material, initially dissolved in the cleaning fluid 4, tends to become re-deposited on the surface of the substrate 5 upon removal of the substrate 5 from the cleaning chamber 2. This adversely affects the yield of devices on the substrate 5. Accordingly, a cleaning tool is needed for both thoroughly cleaning organic films and potential device-contaminating particles from substrates and preventing re-deposition of the films and particles on the substrates during the cleaning process.
An object of the present invention is to provide a new and improved tool for cleaning substrates.
Another object of the present invention is to provide a new and improved tool which is effective in removing potential device-contaminating particles from substrates and preventing the particles from falling back onto the substrates during a substrate-cleaning process.
Still another object of the present invention is to provide a new and improved tool which is effective in removing polymer films from substrates while preventing re-deposition of the films on the substrates during a substrate-cleaning process.
Yet another object of the present invention is to provide a new and improved tool which is effective in thoroughly cleaning potential device-contaminating particles and polymer films from substrates and preventing re-deposition of the particles or films on the substrates during a substrate-cleaning process.
A still further object of the present invention is to provide a new and improved method of effectively cleaning particles and removing polymer films from substrates and preventing substrate re-contamination and film deposition on the substrates.
Yet another object of the present invention is to provide a new and improved tool and method for cleaning substrates, which tool and method utilizes a rapidly-flowing fluid to clean organic films and particles from the substrates.
Another object of the present invention is to provide an all-purpose cleaning tool for substrates.
A still further object of the present invention is to provide a cleaning tool which is capable of utilizing a variety of liquids or gases to clean substrates.